In the present state of the art, vapor compression systems are used in a number of applications to cool an environment. Vapor compression is used in air conditioners, refrigerators, freezers, blast freezers and other cooling systems. Cooling is achieved by evaporating a refrigerant or refrigeration media under reduced pressure to lower the temperature of the refrigerant and absorb heat from an environment.
In conventional vapor compression systems, refrigerants or refrigerant mixtures with low boiling points are used as the working fluid. The refrigerant is pumped to a compressor which elevates the temperature and pressure of the refrigerant. The hot refrigerant is discharged to a first heat exchanger, or condenser, to remove heat from the refrigerant. As heat is removed in the condenser at elevated pressure, the refrigerant converts to the liquid phase. The refrigerant is then conveyed to an expansion valve that rapidly reduces the pressure of the refrigerant. The rapid pressure reduction causes the refrigerant to flash into a liquid and vapor mixture having a very low temperature. The refrigerant is discharged to a second heat exchanger, or evaporator, where the refrigerant absorbs heat. The added heat converts a substantial portion of the remaining liquid phase to the vapor phase. The refrigerant is cycled back to the compressor, where the foregoing process is repeated.
A significant problem with present vapor compression systems is the excessive cost of operation. Vapor compression consumes a significant amount of energy. Energy efficiency in vapor compression systems is often limited by incomplete or inefficient evaporation and condensation of the refrigerant. When evaporation is incomplete, some of the refrigerant enters the compressor shell in the liquid phase. The compressor must consume additional energy to boil the liquid refrigerant that enters the compressor shell. This reduces the coefficient of performance (COP) of system components and overall efficiency of the system.